Laser processing apparatus

Abstract

A laser processing apparatus is disclosed. The disclosed laser processing apparatus comprises: a laser device; a chuck table comprising a first surface, which comprises a curved surface and is a surface on which a workpiece is placed, and a second surface which is at the opposite side to the first surface; a suction unit for adhering the workpiece to the first surface of the chuck table; and a focusing optical system for focusing a pulsed laser beam, provided from the laser device, into the interior of the workpiece placed on the chuck table. The laser device generates a pulsed laser beam, each pulse having a waveform in which, with respect to the peak of the laser beam, the front slope is gentle, and the rear slope is steeper than the front slope.

Description

Laser processing device

[0001] It is about laser processing equipment.

[0002] The semiconductor process of manufacturing semiconductor devices using semiconductor materials such as silicon can be divided into semiconductor pre-process and semiconductor post-process. The semiconductor pre-process may include a process of forming a desired circuit pattern on a semiconductor wafer (e.g., a silicon wafer) using photolithography technology and forming multiple semiconductor devices to be manufactured, such as transistors and light-emitting devices. The semiconductor post-process may include a cutting process of cutting a semiconductor wafer on which multiple semiconductor devices have been formed into chips, and a packaging process of packaging the multiple cut semiconductor chips.

[0003] In these laser processing technologies, it is necessary to generate a sufficient number of cracks to improve the cutting power of semiconductor wafers.

[0004] A laser processing device capable of generating cracks sufficient to cut a processing object while minimizing the number of times a process is performed to form a modified area inside the processing object is performed is provided.

[0005] A laser processing device according to one type includes: a laser device that generates a pulsed laser beam shaped into a shape in which a forward slope relative to a peak of a pulsed laser beam is gentle and a backward slope is steeper than the forward slope; a chuck table that includes a first surface including a curved surface as a surface on which a processing object is placed and a second surface facing the first surface; an adsorption unit that adsorbs the processing object onto the first surface of the chuck table; a focusing optical system that focuses a pulsed laser beam provided from the laser device onto the inside of the processing object placed on the chuck table; a displacement measuring sensor that measures a displacement of an upper surface of the processing object placed on the first surface of the chuck table; and a focusing optical system position control unit that controls a position of the focusing optical system so that a position of a focusing point of the pulsed laser light is adjusted according to the displacement of the upper surface of the processing object measured by the displacement measuring sensor.

[0006] When the pulse width of the pulse laser beam is Tp, the forward width reaching the peak is T1, and the backward width thereafter is T2, the pulse laser beam can satisfy the condition of T1 > T2 (wherein, Tp = T1 + T2).

[0007] The ratio of T1 to Tp (T1 / Tp) may be 0.7 or greater.

[0008] The laser device may include a pulse beam generator that generates a shaped pulse laser beam; a first optical amplifier that amplifies the pulse laser beam generated from the pulse beam generator; and a control unit that controls the pulse beam generator to generate the shaped pulse laser beam in a shape in which the forward slope relative to the peak value of the pulse laser beam is gentle and the backward slope is steeper than the forward slope.

[0009] The pulse beam generating unit may include a laser element that generates a pulse laser beam, and may be configured to generate the pulse laser beam formed from the laser element by applying a control signal from the control unit.

[0010] The pulse beam generating unit includes a light source unit that generates a pulse laser beam; and an optical modulator that shapes the pulse laser beam generated from the light source unit; and by applying a control signal from the control unit to the optical modulator, the pulse laser beam generated from the light source unit can be shaped by the optical modulator.

[0011] The above light source unit may include a pumping laser element that provides a pump beam, and a second optical amplifier unit having a gain medium that amplifies the pump beam to generate the pulsed laser beam.

[0012] The above light source unit may further include a coupler that couples the pump beam onto the path of the second optical amplifier unit.

[0013] The above gain medium includes a gain optical fiber, and the second optical amplifier further includes a pair of optical fiber Bragg gratings arranged on both sides of the gain optical fiber, and light transmission within the pulse beam generator can be achieved through the optical fiber.

[0014] At least one of a first isolator between the pulse beam generator and the first optical amplifier, and a second isolator at the output terminal of the first optical amplifier may be further included.

[0015] The first optical amplifier includes a gain medium that amplifies the pulse laser beam with a pump beam provided from a pumping laser element; and a coupler that couples the pump beam onto a path of the pulse laser beam; the gain medium includes a gain optical fiber, and light transmission within the first optical amplifier can be performed through the optical fiber.

[0016] The above adsorption unit can adsorb the object to be processed onto the chuck table so that the lower surface of the object to be processed is bent to have a shape corresponding to the first surface.

[0017] The above first surface may have a concave shape with the center recessed toward the above second surface.

[0018] The second surface may be formed flat, and the curved surface may be formed such that the distance between the center region of the curved surface and the second surface is closer than the distance between the edge region of the curved surface and the second surface.

[0019] The height difference between the center region of the above-mentioned curved surface and the edge region of the above-mentioned curved surface may be 10 μm to 1500 μm.

[0020] The radius of curvature of the above curved surface may be 10 m to 250 m.

[0021] The above curved surface may include a porous vacuum suction surface, and the suction unit may include a suction pump that sucks air through suction holes formed on the curved surface.

[0022] It may further include a stage connected to the chuck table and configured to be capable of two-dimensional plane movement; and a stage position control unit that controls two-dimensional plane movement of the stage.

[0023] The above-described focusing optical system position control unit can adjust the position of the focusing optical system in the thickness direction of the processing object so that a first distance between a first focusing point and the upper surface of the processing object when the stage is located at a first position by the stage position control unit and a second distance between a second focusing point and the upper surface of the processing object when the stage is located at a second position different from the first position by the stage position control unit are equal.

[0024] The displacement measuring sensor may further include a displacement measuring light source that irradiates light to the processing object and a light receiving element that receives light emitted from the displacement measuring light source and reflected by the processing object, and a dichroic mirror that reflects light from the laser device and transmits light from the displacement measuring light source.

[0025] According to the laser processing device according to the embodiment, when a pulse laser beam is irradiated once, a shaped pulse laser beam that can generate a long uniform length is applied, and further, a chuck table including a curved surface can be utilized to physically extend a crack, so that cutting power can be improved, and the number of laser beam irradiations for cutting a processing object can be reduced, so that processing time can be shortened.

[0026] Fig. 1 schematically shows a laser processing device according to an embodiment.

[0027] Figure 2 is a plan view schematically illustrating an exemplary configuration of the processing object of Figure 1.

[0028] Figures 3 and 4 show examples of the pulse beam generator of Figure 1.

[0029] Figure 5 is for explaining a method of forming a modified area inside a processing target.

[0030] Figure 6 is intended to explain the principle of cracks occurring inside a processing target.

[0031] Figure 7 is for explaining a method of forming multiple cutting lines inside a processing target.

[0032] Figure 8 shows an example of configuring the laser device of Figure 1 to transmit light through an optical fiber.

[0033] Figure 9 shows another example in which the laser device of Figure 1 is configured to transmit light through an optical fiber.

[0034] Fig. 10a shows the waveform of a pulsed laser beam formed by a laser device according to an embodiment (waveform of an embodiment), and shows the relationship between the front width and the rear width of the waveform.

[0035] Figure 10b shows the waveform of a Gaussian pulse laser beam corresponding to the basic waveform (waveform of Comparative Example 1), and shows the relationship between the front width and the rear width of the waveform.

[0036] Figure 10c shows the waveform of the pulse laser beam of Comparative Example 2 (waveform of Comparative Example 2), and shows the relationship between the front width and the rear width of the waveform.

[0037] Figures 11a to 11c are graphs showing the results of evaluating the amount of cracks according to the power (unit: W) and defocus of the pulsed laser beam of Examples, Comparative Examples 1 and 2.

[0038] Figure 12 shows a comparison of the length of a crack according to the pulse width and pulse rise time of a shaped pulse laser beam (example waveform) formed by a laser device according to an embodiment.

[0039] Figures 13a to 13c are graphs showing the results of evaluating the scattered beam by defocus when the pulse laser beam has a high output of 2 W or more.

[0040] Figures 14a to 14c are graphs showing the BHC (Backside half cut) generation height at frequencies of 100 kHz, 120 kHz, and 140 kHz when applying a pulse laser beam of the basic waveform (Comparative Example 1).

[0041] Figures 15a to 15c are graphs showing the BHC generation height at frequencies of 100 kHz, 120 kHz, and 140 kHz when a pulse laser beam of an exemplary waveform is applied.

[0042] Fig. 16 is for explaining the configuration of the chuck table included in the laser processing device of Fig. 1.

[0043] Figure 17 is for explaining the appearance of the workpiece being absorbed into the chuck table.

[0044] Figure 18 is for explaining the appearance of the workpiece placed on the chuck table after laser processing is completed.

[0045] Fig. 19 is a flowchart for explaining a laser processing method according to an embodiment.

[0046] Hereinafter, exemplary embodiments will be described in detail with reference to the attached drawings. In the drawings below, like reference numerals designate like components, and the sizes of each component in the drawings may be exaggerated for clarity and convenience. The embodiments described below are merely exemplary, and various modifications are possible from these embodiments.

[0047] Hereinafter, the terms "upper" or "upper" may include not only those directly above, below, left, or right in contact, but also those directly above, below, left, or right in non-contact. Singular expressions include plural expressions unless the context clearly indicates otherwise. Furthermore, when a part is said to "include" a component, this does not exclude other components, but rather includes other components, unless otherwise specifically stated.

[0048] The use of the term "above" and similar referential terms may refer to both the singular and the plural. Unless the steps of a method are explicitly stated in a specific order or to the contrary, the steps may be performed in any appropriate order, and the order stated is not necessarily limited to that order.

[0049] Additionally, terms such as “part”, “module”, etc. described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software, or a combination of hardware and software.

[0050] The lines connecting or disconnecting between components depicted in the drawings are merely representative of functional connections and / or physical or circuit connections, and may be replaced or represented as various additional functional connections, physical connections, or circuit connections in an actual device.

[0051] Any use of examples or exemplary terms is merely intended to elaborate technical ideas and is not intended to limit the scope of the invention unless otherwise defined by the claims.

[0052] A laser processing device is a device that uses a condenser lens to focus a laser beam into a single focus and irradiates the focus onto the surface or interior of a processing target to process the beam. According to an embodiment, the laser processing device can lengthen the crack length upon a single irradiation by modifying the pulse shape of the laser beam, and can also physically extend the crack by utilizing a chuck table including a curved surface, thereby improving processing performance and reducing processing time.

[0053] The laser processing device according to the embodiment can be applied to, for example, a stealth dicing type laser processing device that forms a modified region by focusing laser light inside a semiconductor wafer during a cutting process included in a semiconductor post-process, and causes the semiconductor wafer to be cut by cracks generated from the modified region. In addition, the laser processing device according to the embodiment can be applied to various types of laser processing devices that require improved processing performance.

[0054] Fig. 1 schematically illustrates a laser device (10) and a laser processing device (100) according to an embodiment. Fig. 2 is a plan view schematically illustrating an exemplary configuration of a processing object (1) of Fig. 1.

[0055] Referring to FIG. 1, the laser processing device (100) includes a laser device (10) that emits a shaped pulse laser beam (Ls), a chuck table (120) that includes a first surface (120a) including a curved surface as a surface on which a processing object (1) is placed, and a second surface (120b) facing the first surface (120a), an adsorption unit (130) that adsorbs the processing object (1) to the first surface (120a) of the chuck table (120), a focusing optical system (110) that focuses the shaped pulse laser beam provided from the laser light source (10) onto the inside of the processing object (1) placed on the chuck table (120), a displacement measuring sensor (150) that measures the displacement of the upper surface of the processing object (1) placed on the first surface (120a) of the chuck table (120), and a pulse laser according to the displacement of the upper surface of the processing object (1) measured by the displacement measuring sensor (150). The laser processing device (100) may include a focusing optical system position control unit (160) that controls the position of the focusing optical system (110) so that the position of the focusing point of the beam is adjusted. In addition, the laser processing device (100) may further include a stage (3) connected to a chuck table (120) and a stage position control unit (170) that controls the position of the stage (3). The laser processing device (100) according to the embodiment may perform a processing process, for example, a cutting process, by irradiating a shaped pulse laser beam (Ls) generated from the laser device (10).

[0056] The processing object (1) may include a semiconductor wafer. The processing object (1) may include a semiconductor wafer made of a silicon semiconductor material or a semiconductor wafer made of another material. For example, referring to FIG. 2, the processing object (1) may include a semiconductor wafer having a plurality of functional elements (2) two-dimensionally arranged on the upper portion. However, the present invention is not limited thereto, and the processing object (1) may not include a plurality of functional elements (2) on the semiconductor wafer.

[0057] The plurality of functional elements (2) may include any one of a light-receiving element such as a photodiode, a light-emitting element such as a laser diode, and a circuit element such as a logic element or a memory element. However, the present invention is not limited thereto, and the plurality of functional elements (2) may include various types of elements other than the above-described elements. The object to be processed (1) may be cut along a cutting line (L) that demarcates an area in which the plurality of functional elements (2) are provided. The cutting line (L) may include a structure in which a plurality of first lines extending in a first direction and arranged parallel to a second direction perpendicular to the first direction and a plurality of second lines extending in a second direction and arranged parallel to the first direction intersect each other. In this case, the first direction and the second direction may be perpendicular to each other. However, the present invention is not limited thereto, and the first direction and the second direction may not be perpendicular to each other.

[0058] The laser device (10) can emit a pulsed laser beam that is transparent to the object to be processed (1). In addition, the laser device (10) can emit a pulsed laser beam that has conditions under which multiphoton absorption can occur within the object to be processed (1) when the pulsed laser beam is focused on the object to be processed (1). The conditions under which multiphoton absorption can occur are widely known in the stealth dicing technology field, and therefore, a description thereof is omitted herein.

[0059] A laser device (10) according to an embodiment may include a pulse beam generator (20) that generates a shaped pulse laser beam, an optical amplifier (50) that amplifies the pulse laser beam generated by the pulse beam generator (20), and a control unit (11) that controls the pulse beam generator (20) to generate the shaped pulse laser beam. The laser device (10) may output a pulse laser beam (Ls), and the pulse laser beam (Ls) may be amplified compared to a pulse laser beam (Ls') generated by the pulse beam generator (20). The pulse laser beam generated by the laser device (10) according to the embodiment has an intensity-variable waveform, and may have a pulse waveform of a Gaussian shape or a similar shape. For example, a pulse laser beam before beam shaping may have a pulse waveform of a Gaussian shape, and the waveform of the pulse laser beam may be modified by beam shaping. By a control signal applied from the control unit (11), the pulse beam generator (20) can be controlled to generate a pulse laser beam shaped into a shape in which the forward slope based on the peak value of the pulse laser beam is gentle and the backward slope is steeper than the forward slope, as exemplarily shown in FIG. 10a described below. In FIG. 1, Ls' represents a shaped pulse laser beam generated from the pulse beam generator (20), and Ls represents a shaped pulse laser beam output from the laser device (10) via the optical amplifier (50).

[0060] Figures 3 and 4 exemplarily show embodiments of the pulse beam generator (20) of Figure 1.

[0061] Referring to FIG. 3, the pulse beam generating unit (20) includes a laser element (LD) 21 that generates a pulse laser beam, and may be arranged to generate a pulse laser beam (Ls') shaped in the laser element (21) in a direct modulation manner. In the present embodiment, the control unit (11) applies a control signal to the laser element (21), and the laser element (21) may be controlled to generate a pulse laser beam (Ls') shaped in a shape in which a forward slope based on a peak value of the pulse laser beam is gentle and a backward slope is steeper than the forward slope. The shaped pulse laser beam (Ls') generated in the laser element (21) may be a beam that is modified to have a gentle forward slope with respect to an intensity-variable pulse beam, for example, a pulse beam having a Gaussian waveform.

[0062] In this way, the pulse beam generating unit (20) of the laser device (10) according to the embodiment may be arranged to apply a control signal to the laser element (21) to output a shaped pulse laser beam (Ls') from the laser element (21). The shaped pulse laser beam (Ls') output from the pulse beam generating unit (20) is input to the optical amplifier unit (50), and may be amplified in the optical amplifier unit (50) to output a shaped pulse laser beam (Ls). The pulse laser beam (Ls) output from the laser device (10), like the shaped pulse laser beam (Ls'), may have a gentle forward slope, a steeper backward slope than the forward slope, and may be a beam whose peak value increases by the amplification rate of the optical amplifier unit (50).

[0063] As another example, referring to FIG. 4, the pulse beam generating unit (20) may include a light source unit (30) that generates a pulse laser beam, and a light modulator (40) that shapes the pulse laser beam generated from the light source unit (30). In the present embodiment, the control unit (11) may apply a control signal to the light modulator (40), and the light modulator (40) may be controlled to shape the pulse laser beam input from the light source unit (30) into a shape in which the forward slope relative to the peak value is gentle and the backward slope is steeper than the forward slope, and output the shaped pulse laser beam (Ls').

[0064] The light source unit (30) may include an optical amplifier unit (25) that amplifies a pump beam provided from a pumping laser element (26), as exemplarily shown in Fig. 9. The pump beam may be a pulse beam, for example, a pulse beam having a Gaussian waveform or a pulse beam having a variable intensity.

[0065] The optical modulator (40) may include, for example, an acousto-optic modulator (AOM). During the beam shaping mode, the optical modulator (40), for example, the acousto-optic modulator, may be maintained in an on state. The control signal of the control unit (11) may be provided to the acousto-optic modulator as electrical power, for example, RF power. Pulsed laser beam shaping may be achieved by adjusting the electrical power, for example, RF power, applied to the acousto-optic modulator. The shaped pulsed laser beam (Ls') may be output from the optical modulator (40), for example, the acousto-optic modulator. As another example, the optical modulator (40) may include a spatial light modulator (SLM). The spatial light modulator may include a silicon substrate, a driving circuit, pixel electrodes, etc., and may adjust the phase of the laser light by adjusting the voltage applied to each pixel electrode, and may modulate the input laser pulse into a desired shape.

[0066] In this way, the laser device (10) according to the embodiment can generate a shaped pulse laser beam (Ls') in the pulse beam generating unit (20), amplify this in the optical amplifier unit (50), and output the shaped pulse laser beam (Ls). The pulse laser beam (Ls) output from the laser device (10) can be a beam that has a gentle forward slope, a steeper backward slope than the forward slope, and a peak value increased by the amplification rate of the optical amplifier unit (50), similar to the shaped pulse laser beam (Ls').

[0067] Meanwhile, the laser device (10) according to the embodiment may be configured to transmit light through an optical fiber (37), as exemplarily shown in FIGS. 8 and 9 described below. A more detailed description of the laser device (10) applied to the laser processing device (100) according to the embodiment will be described below with reference to FIGS. 8 to 15c.

[0068] Referring again to FIG. 1, the shaped pulse laser beam (Ls) output from the laser device (10) can be focused inside the processing target (1) provided on the chuck table (120) by the focusing optical system (110). The laser processing device (100) according to the embodiment can perform a processing process, for example, a cutting process, by irradiating the processing target (1) with the shaped pulse laser beam (Ls) output from the laser device (10).

[0069] In the laser processing device (100) according to the embodiment, the chuck table (120) may include a first surface (120a) to which the processing object (1) is raised, and a second surface (120b) facing the first surface (120a). The first surface (120a) may include a curved surface. For example, the first surface (120a) may have a concave shape in which the center is sunken toward the second surface (120b). Unlike the first surface (120a), the second surface (120b) may be formed flat. However, the present invention is not limited thereto, and the second surface (120b) may also include a curved surface similar to the first surface (120a). A more detailed description of an exemplary shape of the chuck table (120) will be described below with reference to FIG. 16.

[0070] The suction unit (130) may be configured to be connected to the chuck table (120) and to suck air through suction holes formed on the first surface (120a) of the chuck table (120). For example, the suction unit (130) may include a suction pump. Due to the suction force of the suction unit (130), the object to be processed (1) may be sucked onto the first surface (120a) of the chuck table (120). While laser processing is taking place, the object to be processed (1) may be sucked onto the first surface (120a) of the chuck table (120) and stably fixed thereto.

[0071] The focusing optical system (110) may include an optical device that focuses a shaped pulse laser beam (Ls) emitted from a laser device (10) onto the inside of a processing target (1). The focusing optical system (110) may be provided on a chuck table (120) and may focus the pulse laser beam (Ls) emitted from the laser device (10) onto the inside of the processing target (1) provided on the chuck table (120). For example, the focusing optical system (110) may include an optical lens that focuses the pulse laser beam (Ls) onto a focusing point inside the processing target (1).

[0072] The displacement measuring sensor (150) can measure the displacement of the upper surface of the processing object (1) by capturing an image of the surface of the processing object (1). The displacement measuring sensor (150) may include a displacement measuring light source (151) that emits displacement measuring light toward the upper surface of the processing object (1) and a light receiving element (152) that receives the reflected light of the displacement measuring light reflected from the upper surface of the processing object (1). For example, the displacement measuring light source (151) may emit infrared light. However, the present invention is not limited thereto, and the displacement measuring light source (151) may emit various types of light other than infrared light.

[0073] Based on information about light received by the light receiving element (152), a processor (not shown) can calculate the displacement of the upper surface of the processing object (1). For example, when the processing object (1) moves relative to the light collecting optical system (110) along the cutting line (L), the displacement measuring sensor (150) can acquire displacement data of the upper surface of the processing object (1) along the cutting line (L).

[0074] Meanwhile, the laser processing device (100) may further include a dichroic mirror (101) that reflects a pulsed laser beam (Ls) from the laser device (10) and transmits light from a light source (151) for measuring displacement. The dichroic mirror (101) can reflect the pulsed laser beam (Ls) from the laser device (10) and transmit it to a light collection optical system (110), and transmit the light from the light source (151) for measuring displacement and transmit it to the light collection optical system (110). Furthermore, the dichroic mirror (101) can transmit the reflected light of the light for measuring displacement reflected from the object to be processed (1) and transmit it to a light receiving element (152).

[0075] The focusing optical system position control unit (160) can change the position of the focusing optical system (110) in the optical axis direction (z direction). When the laser processing device (100) performs laser processing by focusing a pulsed laser beam (Ls) inside the object to be processed (1), the focusing optical system position control unit (160) can drive a driving unit (not shown) based on displacement data of the upper surface of the object to be processed (1) acquired by the displacement measuring sensor (150) to reciprocate the focusing optical system (110) in the optical axis direction so as to follow the curvature of the upper surface of the object to be processed (1). For example, the focusing optical system (110) can be moved so that the pulsed laser beam (Ls) from the laser device (10) is focused at a certain depth from the upper surface of the object to be processed at any point on the object to be processed (1).

[0076] The stage position control unit (170) can control the movement of the stage (3) connected to the chuck table (120) on which the workpiece (1) is placed. The stage (3) can be configured to be able to move in a two-dimensional plane (xy plane). The stage position control unit (170) can control the movement of the stage (3) on the two-dimensional plane.

[0077] Fig. 5 is for explaining a method for forming a modified region (4) inside a processing object (1). Fig. 6 is for explaining the principle of generating a crack (c1) inside a processing object (1). Fig. 7 is for explaining a method for forming a plurality of cutting lines (5, 6) inside a processing object (1).

[0078] For example, referring to FIG. 5, a pulsed laser beam as processing light can be focused inside a processing object (1). When the stage position control unit (170) moves the stage (3) along the cutting line (L) and focuses the pulsed laser beam inside the processing object (1), the pulsed laser beam can be sequentially focused on a plurality of focusing points arranged in parallel along the cutting line (L) inside the processing object (1). Accordingly, a plurality of modified regions (4) arranged along the cutting line (L) can be formed inside the processing object (1). The plurality of modified regions (4) arranged along the cutting line (L) can form one cutting line.

[0079] Referring to Fig. 6, a plurality of cracks (c1) may be generated based on each of a plurality of modified regions (4). The plurality of cracks (c1) may occur in the process of cooling the plurality of modified regions (4) heated by laser processing. However, the present invention is not limited thereto, and a plurality of cracks (c1) may also be generated when an external stress acts on the plurality of modified regions (4). The plurality of cracks (c1) may extend to reach the upper surface (1a) and the lower surface (1b) of the object to be processed (1). The object to be processed (1) may be cut based on the plurality of cracks (c1).

[0080] Also, referring to FIG. 7, a plurality of cutting lines (5, 6) provided at different positions in the optical axis direction (z direction) inside the processing target (1) can be formed. For example, by performing laser processing in a state where the focusing optical system (110) is provided at a first position and a state where the focusing optical system (110) is provided at a second position which is different from the first position in the optical axis direction (z direction) by the focusing optical system position control unit (160), a plurality of cutting lines (5, 6) provided at different positions in the optical axis direction (z direction) can be formed. The plurality of cutting lines (5, 6) can be formed with a time difference. However, the present invention is not limited thereto, and the plurality of cutting lines (5, 6) can be simultaneously formed by a branched pulse laser beam. In order to form a plurality of cutting lines (5, 6) using a branched pulse laser beam, the laser processing device (100) can include two or more focusing optical systems.

[0081] As illustrated in Fig. 7, when forming multiple cutting lines (5, 6) at different positions in the optical axis direction (z direction) inside the processing object (1), sufficient cracks can be generated to cut the processing object (1). However, the process time required to form multiple cutting lines (5, 6) may be long, or a separate optical system may be required to generate branched light necessary to form multiple cutting lines (5, 6).

[0082] Hereinafter, a laser device (10) applied to a laser processing device (100) according to an embodiment will be described in detail with reference to FIGS. 8 to 15c.

[0083] Fig. 8 shows an example of a configuration in which the laser device (10) of Fig. 1 is configured to transmit light through an optical fiber (37). Fig. 8 shows an example in which the laser device (10) has a configuration in which the pulse beam generator (20) of Fig. 3 is applied.

[0084] Referring to FIG. 8, a laser device (10) according to an embodiment includes a pulse beam generating unit (20) that generates a shaped pulse laser beam and an optical amplifying unit (50), and light transmission within the laser device (10) can be arranged to be performed through an optical fiber (37).

[0085] The pulse beam generating unit (20) includes a laser element (21) that generates a pulse laser beam, as described with reference to FIG. 3, and may be arranged to output a pulse laser beam shaped from the laser element (21) in a direct modulation manner. A control signal from the control unit (11) is applied to the laser element (21), and a pulse laser beam (Ls') shaped from the laser element (21) may be generated. The shaped pulse laser beam (Ls') output from the laser element (21) may be transmitted to the optical amplifier (50) using an optical fiber (37) as a transmission path. The pulse laser beam (Ls') may be amplified and output from the optical amplifier (50).

[0086] The optical amplification unit (50) may be formed as a single structure or may include a plurality of optical amplification units (51)(55), and light transmission within the optical amplification unit (50) may be arranged to be performed, for example, through an optical fiber (37). As exemplarily shown in FIG. 8, when a plurality of optical amplification units (51)(55) are included, an isolator (33) may be further provided between the optical amplification units (51)(55) to prevent reverse transmission of light between the optical amplification units (51)(55). FIG. 8 shows an example in which the optical amplification unit (50) includes two optical amplification units (51)(55), and an isolator (33) is provided between the two optical amplification units (51)(55).

[0087] The optical amplifier (51)(55) may include a gain medium (54)(58) that amplifies a pulsed laser beam transmitted from a pulsed beam generator (20) using a pump beam provided from a pumping laser element (52)(56), and a coupler (53)(57) that couples the pump beam onto the propagation path of the pulsed laser beam. The gain medium (54)(58) may amplify the pulsed laser beam using the pump beam on the propagation path of the pulsed laser beam. The gain medium (54)(58) may include a gain optical fiber as exemplarily shown in FIG. 8. The gain optical fiber may be, for example, an optical fiber doped with a gain element so that the pulsed laser beam is amplified through stimulated emission from atoms excited by the pump beam.

[0088] Meanwhile, an isolator (31) may be further provided between the pulse beam generator (20) and the optical amplifier (50) to prevent reverse transmission of light from the optical amplifier (50) to the pulse beam generator (20). In addition, when the optical amplifier (50) output terminal, for example, a plurality of optical amplifiers (51) and (55), an isolator (35) may be further provided at the final optical amplifier (55) output terminal to prevent reverse transmission of light from the outside to the laser device (10).

[0089] In Fig. 8, it is illustrated that two amplifier units (51)(55) are provided, but this is not limited thereto. The amplifier unit (50) may be configured to have a single structure or include three or more amplifier units.

[0090] Fig. 9 shows another example in which the laser device (10) of Fig. 1 is configured to transmit light through an optical fiber (37). Fig. 9 shows an example in which the laser device (10) has a configuration in which the pulse beam generator (20) of Fig. 4 is applied.

[0091] Referring to FIG. 9, a laser device (10) according to an embodiment includes a pulse beam generating unit (20) that generates a shaped pulse laser beam and an optical amplifying unit (50), and light transmission within the laser device (10) can be arranged to be performed through an optical fiber (37).

[0092] The pulse beam generating unit (20) may include a light source unit (30) that generates a pulse laser beam, and a light modulator (40) that shapes the pulse laser beam generated from the light source unit (30). In the present embodiment, the control unit (11) applies a control signal to the light modulator (40), and the light modulator (40) may be controlled to shape the pulse laser beam generated from the light source unit (30) into a shape in which the forward slope based on the peak value is gentle and the backward slope is steeper than the forward slope.

[0093] The light source unit (30) may include a pumping laser element (26) that provides a pump beam, and an optical amplifier unit (25) that amplifies the pump beam provided from the pumping laser element (26). The light source unit (30) may further include a coupler (27) that couples the pump beam onto the path of the optical amplifier unit (25). Here, the pump beam may be a pulse beam, for example, a pulse beam having a Gaussian waveform or a pulse beam having a variable intensity.

[0094] The optical amplifier (25) may include a gain medium (28) that amplifies a pump beam provided from a pumping laser element (26). The gain medium (28) may generate an amplified pulse laser beam using the pump beam. The gain medium (28) may include a gain optical fiber as exemplarily shown in FIG. 9. The gain optical fiber may be, for example, an optical fiber doped with a gain element so that beam amplification is achieved through stimulated emission from atoms excited by the pumping beam.

[0095] Meanwhile, the optical amplification unit (25) may further include a pair of optical fiber Bragg gratings (29a) (29b) arranged on both sides of the gain medium (28). The optical fiber Bragg grating (29a) (29b) is, for example, an optical fiber that reacts (transmits, reflects, etc.) only to a specific wavelength in a narrow range that satisfies the Bragg condition, and has a grating structure in which the effective refractive index in the optical fiber core is periodically or aperiodically changed in the direction of the optical fiber axis. By arranging the optical fiber Bragg gratings (29a) (29b) on both sides of the gain medium (28), only the wavelength band that satisfies the Bragg condition can be transmitted and reflected. Since a part of the pulse laser beam is reflected by the optical fiber Bragg gratings (29a) (29b) and re-passes through the gain medium (28), the amplification ratio in the optical amplification unit (50) can be increased. In addition, by providing the optical fiber Bragg gratings (29a) (29b), the wavelength linewidth of the pulse laser beam can be reduced.

[0096] The pump beam provided from the pumping laser element (26) can be amplified in the optical amplifier (25) and transmitted to the optical modulator (40) as a pulse laser beam.

[0097] The optical modulator (40) can be controlled by the control unit (11) to shape the pulse laser beam generated from the light source unit (30) into a shape in which the forward slope is gentle and the backward slope is steeper than the forward slope based on the peak value. Here, the pulse laser beam before shaping can be an intensity-variable pulse beam, for example, a pulse beam with a Gaussian waveform.

[0098] The optical modulator (40) may include, for example, an acoustic optical modulator. During the beam shaping mode, the optical modulator (40), for example, the acoustic optical modulator, may be maintained in an on state. The control signal of the control unit (11) may be provided to the acoustic optical modulator as electrical power, for example, RF power. Pulsed laser beam shaping may be achieved by adjusting the electrical power, for example, RF power, applied to the optical modulator (40), for example, the acoustic optical modulator. As another example, the optical modulator (40) may include a spatial light modulator (SLM). The spatial light modulator may include a silicon substrate, a driving circuit, pixel electrodes, etc., and may adjust the phase of the laser light by adjusting the voltage applied to each pixel electrode, and may modulate the input laser pulse into a desired shape.

[0099] In this way, the shaped pulse laser beam (Ls') generated in the pulse beam generator (20) can be transmitted to the optical amplifier (50) using the optical fiber (37) as a transmission path. Then, the shaped pulse laser beam (Ls) can be output by being amplified in the optical amplifier (50).

[0100] FIG. 9 shows an example of a single structure optical amplifier (51) provided as an optical amplifier (50). The optical amplifier (51) may include a gain medium (54) that amplifies a shaped pulse laser beam (Ls') transmitted from a pulse beam generator (20) using a pump beam provided from a pumping laser element (52), and a coupler (53) that couples the pump beam onto the propagation path of the shaped pulse laser beam (Ls'). The gain medium (54) may amplify the pulse laser beam (Ls') using the pump beam on the propagation path of the pulse laser beam (Ls'). As exemplarily shown in FIG. 9, the gain medium (54) may include a gain optical fiber. The gain optical fiber may be, for example, an optical fiber doped with a gain element so that the pulse laser beam (Ls) is amplified through stimulated emission from atoms excited by the pump beam.

[0101] Meanwhile, in FIG. 9, the optical amplification unit (50) is illustrated as having a single structure including an optical amplification unit (51), but the embodiment is not limited thereto. For example, the optical amplification unit (50) may include a plurality of optical amplification units as described above with reference to FIG. 8. In the case where the optical amplification unit (50) includes a plurality of optical amplification units, an isolator may be further provided between the optical amplification units to prevent reverse transmission of light between the optical amplification units as exemplarily shown in FIG. 8.

[0102] Meanwhile, an isolator (31) may be further provided between the pulse beam generator (20) and the optical amplifier (50) to prevent reverse transmission of light from the optical amplifier (50) to the pulse beam generator (20). In addition, when the optical amplifier (50) output terminal, for example, has multiple optical amplifiers, an isolator (35) may be further provided at the final optical amplifier output terminal to prevent reverse transmission of light from the outside to the laser device (10).

[0103] FIG. 8 and FIG. 9 only show examples of configuring a laser device (10) to transmit light through an optical fiber (37), but the embodiment is not limited thereto, and various modifications are possible.

[0104] The laser processing device (100) according to the embodiment can perform a processing process, for example, a cutting process, by irradiating a shaped pulse laser beam (Ls) obtained from the laser device (10) according to the various embodiments described above onto a processing target (1).

[0105] The laser processing device (100) according to the embodiment can be implemented to perform a cutting process, for example, in a stealth dicing manner. For example, the laser processing device (100) according to the embodiment can be used as a semiconductor post-process, by focusing a shaped pulse laser beam (Ls) obtained from the laser device (10) onto an object to be processed (1), for example, a semiconductor wafer, to form a modified region, and cutting the semiconductor wafer by cracks generated from the modified region. In addition, the laser device according to the embodiment can be applied to various types of laser processing devices that require improved processing performance.

[0106] FIG. 10A shows the waveform of a pulsed laser beam formed by a laser device (10) according to an embodiment (waveform of an embodiment), and shows the relationship between the forward width and the backward width of the waveform. The shaped pulsed laser beam obtained by the laser device (10) according to the embodiment is formed as a waveform in which the forward slope based on the peak (P) is gentle and the backward slope is steeper than the forward slope. As in FIG. 10A, when the pulse width of the pulsed laser beam is Tp, the forward width reaching the peak is T1, and the backward width thereafter is T2, the shaped pulsed laser beam obtained by the laser device (10) according to the embodiment satisfies the condition of T1 > T2 (wherein, Tp = T1 + T2). At this time, the ratio of T1 to Tp (T1 / Tp) may be 0.7 or more. For example, T1 / Tp may be about 0.7 to 0.9, about 0.7 to 0.85, or about 0.8 to 0.9. Here, the pulse width of the pulsed laser beam described in FIG. 10a and below may represent, for example, the full width at half maximum.

[0107] Figure 10b shows the waveform of a Gaussian pulse laser beam corresponding to the basic waveform (waveform of Comparative Example 1), and shows the relationship between the front width and the rear width of the waveform.

[0108] The Gaussian pulse laser beam of Comparative Example 1 is formed into a waveform having the same forward slope and backward slope relative to the peak (P). As in Fig. 10b, when the pulse width of the Gaussian pulse laser beam is Tp', the forward width reaching the peak (P) is T1', and the backward width thereafter is T2', the Gaussian pulse laser beam satisfies the condition of T1' = T2' (where, Tp' = T1' + T2').

[0109] Fig. 10c shows the waveform of the pulse laser beam of Comparative Example 2 (waveform of Comparative Example 2), and shows the relationship between the forward width and the backward width of the waveform. The pulse laser beam of Comparative Example 2 is formed as a waveform in which the forward slope is steep with respect to the peak (P) and the backward slope is gentler than the forward slope. As in Fig. 10c, when the pulse width of the pulse laser beam of Comparative Example 2 is Tp”, the forward width reaching the peak (P) is T1”, and the backward width thereafter is T2”, the pulse laser beam of Comparative Example 2 satisfies the condition of T1” < T2” (wherein, Tp” = T1” + T2”).

[0110] Hereinafter, the processing performance when applying the laser device (10) according to the embodiment will be described with reference to FIGS. 11A to 15C. The waveform of the embodiment applied to the processing performance evaluation has a shape in which the forward slope based on the peak (P) is gentle, and the backward slope is steeper than the forward slope, as shown in FIG. 10A. The waveform of the embodiment has a pulse rising time longer than the pulse falling time. The waveform of Comparative Example 1 applied for comparison has a Gaussian shape, as shown in FIG. 10B, and the pulse rising time and falling time are the same. In addition, the waveform of Comparative Example 2 applied for comparison has a shape in which the forward slope based on the peak (P) is steep, the backward slope is gentler than the forward slope, and the pulse falling time is longer than the pulse rising time, as shown in FIG. 10C.

[0111] Figures 11a to 11c are graphs showing the results of evaluating the amount of cracks according to the power (unit: W) and defocus of the pulsed laser beam of Examples, Comparative Examples 1 and 2. Figure 11a shows the change in crack length of the processed sample according to the pulsed laser beam power when the pulsed laser beam is focused to a defocus state of -0.110 mm. Figure 11b shows the change in crack length of the processed sample according to the pulsed laser beam power when the pulsed laser beam is focused to a defocus state of -0.115 mm. Figure 11c shows the change in crack length of the processed sample according to the pulsed laser beam power when the pulsed laser beam is focused to a defocus state of -0.120 mm. In Figures 11a to 11c, the horizontal axis represents the processing power of the pulsed laser beam (unit: W), and the vertical axis represents the crack length (unit: μm).

[0112] Looking at Figures 11a to 11c, when the power of the pulse laser beam is 2 W or less, the crack length does not differ significantly between the waveform of the example and the waveform of Comparative Example 1, but in the high-power section of 2 W or more, it can be confirmed that the crack length in the waveform of the example is longer than that in the waveform of Comparative Example 1 and Comparative Example 2 in all defocuses. In addition, it can be seen that in the waveform of the example, in the high-power section of 2 W or more, the crack length is longest when the defocus is -0.115 mm.

[0113] Therefore, as can be seen from FIGS. 11a to 11c, when a cutting process is performed with an appropriate output power, for example, 2 W to 4 W, using a laser processing device (100) that applies a laser device (10) according to an embodiment, a crack length can be generated long when a pulsed laser beam is irradiated once, so that the number of times the pulsed laser beam is irradiated repeatedly can be reduced during a semiconductor wafer or chip dicing process, thereby shortening the processing time.

[0114] Fig. 12 shows a comparison of the length of a crack according to the pulse width and pulse rise time of a shaped pulse laser beam (example waveform) formed by a laser device (10) according to an embodiment. In Fig. 12, the horizontal axis represents the pulse rise time (unit: ns), and the vertical axis represents the bottom uniform (crack) length (unit: μm). Here, the bottom represents the side opposite to the surface on which semiconductor elements are formed on the wafer. When dicing a wafer into chip units or predetermined block units, the cutting process can be performed on the bottom of the wafer.

[0115] The graph in Fig. 12 shows the relationship between the rise time of the pulse and the uniform length when the pulse widths of the example waveforms are about 360 ns, about 400 ns, about 430 ns, about 460 ns, and about 500 ns, respectively. Gaussian corresponds to the basic waveform (Comparative Example 1) and represents the crack length for a Gaussian waveform pulse with a pulse width of about 320 ns. The length of the crack that occurs when irradiated once is about 62.7 μm.

[0116] Looking at Fig. 12, it can be seen that the pulse width of the example waveform that can make the crack length longer than the basic waveform is larger than the pulse width of the basic waveform. In addition, when the pulse width is approximately 400 ns or more, the crack length by the example waveform becomes almost longer than that by the basic waveform with a pulse width of 320 ns, and it can be seen that the crack length also increases as the pulse width increases. Fig. 12 shows an example where the crack length is the longest when the pulse width is 500 ns and the pulse rise time is 300 ns to 380 ns.

[0117] Therefore, the laser device (10) according to the embodiment and the laser processing device (100) including the same can set the pulse width to secure a desired crack length when the pulse laser beam is irradiated once. In addition, when a cutting process is performed with a pulse laser beam having the pulse width set in this way and having a forward slope that is gentler than a backward slope based on the peak (P), the crack length can be generated longer when the pulse laser beam is irradiated once, so that the number of times the pulse laser beam is irradiated repeatedly can be reduced during a semiconductor wafer or chip dicing process, thereby shortening the processing time.

[0118] Figures 13a to 13c are graphs showing the results of evaluating the scattered beam according to defocus when the pulsed laser beam has a high power of 2 W or more. Figures 13a to 13c show the relationship between the crack length and the scattered beam according to defocus when the pulsed laser beam has high powers of 2.4 W, 2.8 W, and 3.0 W, respectively. As can be seen in Figures 13a to 13c, at a high power of 2 W or more, even though the crack length increases, there is almost no difference in the scattered beam between the basic waveform (Comparative Example 1) and the exemplary waveform, and it can be seen that the scattered beam characteristics of the exemplary waveform are superior to those of the basic waveform (Comparative Example 1) at high power. The crack length is the longest at a defocus of -0.105 mm, but it can be confirmed that the scattered beam exhibits the best characteristics at a defocus of -0.115 mm for the exemplary waveform.

[0119] FIGS. 14a to 14c are graphs showing the BHC (Backside half cut) generation height at each frequency of 100 kHz, 120 kHz, and 140 kHz when applying a pulse laser beam of a basic waveform (Comparative Example 1), and FIGS. 15a to 15c are graphs showing the BHC generation height at each frequency of 100 kHz, 120 kHz, and 140 kHz when applying a pulse laser beam of an example waveform.

[0120] Comparing the graphs of FIGS. 14a to 14c with the graphs of FIGS. 15a to 15c, it can be confirmed that the BHC generation height by frequency is also superior for the exemplary waveform compared to the basic waveform (Comparative Example 1). As described above, the laser device (10) according to the exemplary embodiment generates a pulsed laser beam having a gentle forward slope relative to the peak (P) and a steeper backward slope than the forward slope compared to the basic waveform, which is a Gaussian waveform. Therefore, when the pulsed laser beam is irradiated once, a crack length can be generated longer than when the basic waveform is applied, so that the wafer cutting force and processing speed can be improved, and thus the yield can be improved.

[0121] According to a laser processing device (100) that applies a laser device (10) that generates a pulsed laser beam shaped into a shape in which the forward slope based on the peak is gentle and the backward slope is steeper than the forward slope, when the pulsed laser beam is irradiated once, a uniform length can be generated, so that the cutting power is improved, and thereby the processing time can be shortened.

[0122] In addition, the laser processing device (100) according to the embodiment can further reduce the processing time by physically extending the crack by utilizing a chuck table (120) including a curved surface, as described below.

[0123] Hereinafter, with reference to FIGS. 16 to 18, a method for generating cracks sufficient to cut a workpiece (1) without forming multiple cutting lines provided at different positions in the optical axis direction (z direction) will be described.

[0124] Fig. 16 is for explaining the configuration of the chuck table (120) included in the laser processing device (100) of Fig. 1. Fig. 17 is for explaining the appearance of the object to be processed (1) being absorbed by the chuck table (120). Fig. 18 is for explaining the appearance of the object to be processed (1) placed on the chuck table (120) after laser processing is completed.

[0125] Referring to Fig. 16, a workpiece (1) to be processed can be placed on a first surface (120a) of a chuck table (120). As described above, the first surface (120a) includes a curved surface, and the second surface (120b) can be formed flat. In other words, the first surface (120a) can have a concave shape with its center recessed toward the second surface (120b). However, this is not limited to this, and the second surface (120b) can also be formed to be non-flat.

[0126] For example, the first surface may be formed so as to be further from the flat second surface (120b) from the center toward the edge. In this case, the distance between the central region of the curved surface included in the first surface (120a) and the second surface (120b) may be closer than the distance between the edge region of the curved surface and the second surface (120b). Accordingly, a height difference (d) may exist between the central region and the edge region of the curved surface included in the first surface (120a), and this height difference (d) may be about 10 μm to 1500 μm. For example, the height difference (d) between the central region and the edge region of the curved surface included in the first surface (120a) may be any one of 50 μm, 100 μm, 300 μm, 400 μm, 600 μm, and 1000 μm. In this case, the height difference (d) may be the distance in the optical axis direction (z direction) between the highest point and the lowest point of the first surface (120a).

[0127] The radius of curvature of the curved surface included in the first surface (120a) may be about 10 m to 250 m. For example, the radius of curvature of the curved surface included in the first surface (120a) may be any one of 222010.025 mm, 111005.050 mm, 37001.816 mm, 27751.450 mm, 18501.133 mm, and 11101.000 mm. However, the present invention is not limited thereto, and the radius of curvature of the curved surface included in the first surface (120a) may have various dimensions within the range of 10 m to 250 m.

[0128] Referring to Fig. 17, the workpiece (1) can be adsorbed on the chuck table (120) by the suction force of the suction unit (130). For example, the curved surface included in the first surface (120a) of the chuck table (120) can include a porous vacuum suction surface. In other words, suction holes can be formed in the first surface (120a). The suction unit (130) can include a suction pump that sucks air through the suction holes formed in the first surface (120a). As the workpiece (1) is adsorbed on the chuck table (120) by the suction action of the suction unit (130), the lower surface (1b) of the workpiece (1) can be bent to have a shape corresponding to the first surface (120a) including the curved surface. Similarly, the upper surface (1a) of the workpiece (1) can also be bent.

[0129] As described above, the position of the chuck table (120) on the two-dimensional plane (xy plane) can be changed by the stage position control unit (170). Accordingly, the position of the object to be processed (1) on the two-dimensional plane (xy plane) can be changed. In this case, the object to be processed (1) can move along the cutting line (L), and a cutting line (7) formed parallel to the cutting line (L) can be formed inside the object to be processed (1). The cutting line (7) can include a plurality of modified regions.

[0130] For example, when the stage (3) is positioned at the first position by the stage position control unit (170), the laser light can be focused on any first focusing point (a1) inside the object (1) to be processed. In addition, when the stage (3) is positioned at a second position different from the first position by the stage position control unit (170), the laser light can be focused on any second focusing point (a2) different from the first focusing point (a1) inside the object (1) to be processed. For example, the distance (t1) between the point corresponding to the first focusing point (a1) of the upper surface (1a) and the highest point of the upper surface (1a) may be different from the distance (t2) between the point corresponding to the second focusing point (a2) of the upper surface (1a) and the highest point of the upper surface (1a). If the second focusing point (a2) is closer to the center of the processing object (1) than the first focusing point (a1), the distance (t2) may be greater than the distance (t1).

[0131] The focusing optical system position control unit (160) can adjust the position of the focusing optical system (110) in the thickness direction (z direction) of the processing object (1) so that the first distance (k1) between the first focusing point (a1) and the upper surface (1a) of the processing object (1) and the second distance (k2) between the second focusing point (a2) and the upper surface (1a) of the processing object (1) are equal. In this case, the focusing optical system position control unit (160) can adjust the position of the focusing optical system (110) in the thickness direction (z direction) of the processing object (1) based on the displacement of the upper surface of the processing object (1) measured by the displacement measuring sensor (150). According to the position control of the light-gathering optical system (110) by the light-gathering optical system position control unit (160), the cutting line (7) formed inside the processing object (1) can be formed in a curved shape having the same radius of curvature as the radius of curvature of the first surface (120a).

[0132] Referring to Fig. 18, when the operation of the suction unit (130) is terminated, the workpiece (1) can be separated from the chuck table (120). Accordingly, the workpiece (1) that was warped can be restored to its original shape by elasticity. For example, after the operation of the suction unit (130) is terminated, the workpiece (1) can become flat again like its original shape. In the process of restoring the shape of the workpiece (1) after the operation of the suction unit (130) is terminated, the shape of the cutting line (7) formed to be warped inside the workpiece (1) can be deformed. For example, as illustrated in Fig. 18, as the workpiece (1) becomes flat, a flat cutting line (7') can be formed inside the workpiece (1). In the process of the warped cutting line (7) changing into the flat cutting line (7'), the amount of cracks occurring inside the workpiece (1) can significantly increase. For example, as illustrated in Fig. 7, the amount of cracks generated when a plurality of cutting lines (5, 6) spaced apart in the optical axis direction (z direction) are formed may be similar to the amount of cracks generated in the process in which a single cutting line (7) in the curved optical axis direction (z direction) changes into a flat cutting line (7'). In this way, even when a single cutting line (7), rather than a plurality, is formed in the optical axis direction (z direction) inside the object to be processed (1) using the laser processing device (100), a sufficient amount of cracks can be generated for cutting the object to be processed (1).

[0133] Fig. 19 is a flowchart for explaining a laser processing method according to an embodiment.

[0134] In explaining FIG. 19, reference is made to the components of the laser processing device (100) described with reference to FIG. 1, FIG. 17 to FIG. 18.

[0135] Referring to FIG. 19, a laser processing method according to one embodiment includes a step (S101) of adsorbing a processing object (1) onto a first surface (120a) using an adsorption unit (130) connected to a chuck table (120) so that a lower surface (1b) of the processing object (1) is bent to have a shape corresponding to a first surface (120a) including a curved surface of the chuck table (120), a step (S102) of focusing laser light on a first focusing point (a1) at an arbitrary first position on the upper surface (1a) opposite to the lower surface (1b) of the processing object (1) in contact with the first surface (120a) and a first distance (k1) away from the upper surface (1a) toward the lower surface (1b), and a step (S103) of focusing laser light on an arbitrary second position different from the first position on the upper surface (1a) and at a second distance (k2) away from the upper surface (1a) toward the lower surface (1b). It may include a step (S103) of focusing laser light on a second focusing point (a2) and a step (S104) of terminating the operation of the adsorption unit (130) that adsorbs the processing object (1) onto the first surface (120a) so that the lower surface (1b) of the processing object (1) is spaced apart from the first surface (120a).

[0136] In the step (S101) of adsorbing the object to be processed (1) onto the first surface (120a), air may be sucked through adsorption holes formed in the curved porous vacuum adsorption surface included in the first surface (120a) to adsorb the object to be processed (1) onto the first surface (120a). However, this is not limited thereto, and various methods other than the above-described method may be used to adsorb the object to be processed (1) onto the first surface (120a).

[0137] For example, the suction unit (130) connected to the chuck table (120) may include a suction pump. As the workpiece (1) is sucked onto the first surface (120a) of the chuck table (120) by the suction action of the suction unit (130), the lower surface (1b) of the workpiece (1) may be curved to have a shape corresponding to the first surface (120a) including a curved surface. Similarly, the upper surface (1a) of the workpiece (1) may also be curved.

[0138] Referring to FIGS. 1 and 17, in the step (S102) of focusing laser light on a first focusing point (a1), the laser light can be focused on any first focusing point (a1) inside the processing target (1). The first focusing point (a1) can be a position located a first distance (k1) in the vertical direction (z) from any first position on the upper surface (1a) of the processing target (1) toward the lower surface (1b).

[0139] Referring to FIGS. 1 and 17, in the step (S103) of focusing the laser light on the second focusing point (a2), the laser light can be focused on an arbitrary second focusing point (a2) different from the first focusing point (a1) inside the object to be processed (1). The second focusing point (a2) may be a position that is a second distance (k2) away from an arbitrary second position different from the first position on the upper surface (1a) of the object to be processed (1) toward the lower surface (1b) in the vertical direction (z). For example, the second focusing point (a2) may be a point located on the same cutting line (L) as the first focusing point (a1).

[0140] By repeating the step (S102) of focusing the laser light on the first focusing point (a1) and the step (S103) of focusing the laser light on the second focusing point (a2), the laser light can be focused on a plurality of focusing points located along the cutting line (L). To this end, the object to be processed (1) can be moved along the cutting line (L) and the laser light can be sequentially focused on a plurality of focusing points inside the object to be processed (1). In this case, the object to be processed (1) can be moved by changing the position of the chuck table (120) on which the object to be processed (1) is placed on a two-dimensional plane (xy plane) using the stage position control unit (170). Accordingly, a cutting line (7) formed parallel to the cutting line (L) inside the object to be processed (1) can be formed. The cutting line (7) can include a plurality of modified regions.

[0141] In the step (S104) of terminating the operation of the suction unit (130), for example, the operation of the suction unit (130) that sucks air through the suction hole formed in the first surface (120a) of the chuck table (120) in order to adsorb the object (1) to be processed on the first surface (120a) may be terminated. Accordingly, referring to FIG. 18, the object (1) to be processed that was bent may be restored to its original shape by elasticity. After the operation of the suction unit (130) is terminated, in the process of restoring the shape of the object (1) to be processed, the shape of the cutting line (7) formed to be bent inside the object (1) to be processed may be deformed. For example, as illustrated in FIG. 18, as the object (1) to be processed becomes flat, a flat cutting line (7') may be formed inside the object (1). In the process of the curved cutting line (7) changing into a flat cutting line (7'), the amount of cracks occurring inside the processing target (1) may significantly increase.

[0142] Although the above-described laser device and the laser processing device and laser processing method including the same have been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible from the above. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of this specification is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being included.

Claims

1. A laser device that generates a pulsed laser beam shaped into a shape in which the forward slope is gentle and the backward slope is steeper than the forward slope based on the peak of the pulsed laser beam; A chuck table including a first surface including a curved surface as a surface on which a workpiece is placed and a second surface facing the first surface; An adsorption unit that adsorbs the processing object onto the first surface of the chuck table; A focusing optical system that focuses a pulse laser beam provided from the laser device onto the inside of the processing object placed on the chuck table; A displacement measuring sensor that measures the displacement of the upper surface of the workpiece placed on the first surface of the chuck table; and A laser processing device including a focusing optical system position control unit that controls the position of the focusing optical system so that the position of the focusing point of the pulse laser light is adjusted according to the displacement of the upper surface of the processing object measured by the displacement measuring sensor.

2. In the first paragraph, when the pulse width of the pulse laser beam is Tp, the front width reaching the peak is T1, and the rear width thereafter is T2, The above pulse laser beam is a laser processing device that satisfies the condition of T1 > T2 (wherein, Tp = T1 +T2).

3. A laser processing device in the second paragraph, wherein the ratio of T1 to Tp (T1 / Tp) is 0.7 or more.

4. In the first paragraph, the laser device, A pulse beam generator for generating a shaped pulse laser beam; A first optical amplifier that amplifies a pulse laser beam generated from the pulse beam generator; A laser processing device comprising a control unit that controls the pulse beam generating unit to generate the pulse laser beam shaped into a shape in which the forward slope of the pulse laser beam is gentle and the backward slope is steeper than the forward slope relative to the peak of the pulse laser beam.

5. In the fourth paragraph, the pulse beam generating unit, A laser device comprising a laser element that generates a pulsed laser beam, A laser processing device configured to generate the pulse laser beam formed from the laser element by applying a control signal from the control unit.

6. In the fourth paragraph, the pulse beam generating unit, A light source unit that generates a pulsed laser beam; It includes a light modulator that shapes a pulse laser beam generated from the above light source unit; A laser processing device in which a control signal is applied from the control unit to the optical modulator, thereby shaping a pulse laser beam generated from the light source unit in the optical modulator.

7. In paragraph 6, the light source unit, A laser processing device comprising a pumping laser element providing a pump beam, and a second optical amplifier having a gain medium that amplifies the pump beam to generate the pulsed laser beam.

8. In the 7th paragraph, the light source unit, A laser processing device further comprising a coupler that couples the pump beam onto the path of the second optical amplifier.

9. In the 7th paragraph, the gain medium includes a gain optical fiber, The second optical amplifier further includes a pair of optical fiber Bragg gratings arranged on both sides of the gain optical fiber; A laser processing device in which light transmission within the pulse beam generator is performed via an optical fiber.

10. A laser processing device according to claim 3, further comprising at least one of a first isolator between the pulse beam generator and the first optical amplifier, and a second isolator at the output terminal of the first optical amplifier.

11. In the third paragraph, the first optical amplification unit, A gain medium that amplifies the pulsed laser beam with a pump beam provided from a pumping laser device; and A coupler that couples the pump beam onto the path of the pulse laser beam; The above gain medium includes a gain optical fiber, A laser processing device in which light transmission within the first optical amplification section is performed via an optical fiber.

12. In any one of paragraphs 1 to 11, A laser processing device in which the above adsorption unit adsorbs the processing object to the chuck table so that the lower surface of the processing object is bent to have a shape corresponding to the first surface.

13. In any one of paragraphs 1 to 11, A laser processing device having a concave shape in which the first surface is concave with the center thereof recessed toward the second surface.

14. In any one of paragraphs 1 to 11, A laser processing device in which the second surface is formed flat, and the curved surface is formed such that the distance between the center area of ​​the curved surface and the second surface is closer than the distance between the edge area of ​​the curved surface and the second surface.

15. In paragraph 14, A laser processing device in which the height difference between the center area of ​​the above-mentioned curved surface and the edge area of ​​the above-mentioned curved surface is 10 μm to 1500 μm.

16. In any one of paragraphs 1 to 11, A laser processing device having a radius of curvature of the above-mentioned curved surface of 10 m to 250 m.

17. In any one of paragraphs 1 to 11, The above curved surface includes a porous vacuum suction surface, A laser processing device in which the above suction unit includes a suction pump that sucks air through suction holes formed on the curved surface.

18. In any one of paragraphs 1 to 11, A stage connected to the chuck table and configured to be capable of two-dimensional plane movement; and A laser processing device further comprising a stage position control unit for controlling two-dimensional plane movement of the stage.

19. In the 18th paragraph, the light-gathering optical system position control unit, A laser processing device that adjusts the position of the focusing optical system in the thickness direction of the processing object so that a first distance between a first focusing point and the upper surface of the processing object when the stage is located at a first position by the stage position control unit and a second distance between a second focusing point and the upper surface of the processing object when the stage is located at a second position different from the first position by the stage position control unit are equal.

20. In any one of paragraphs 1 to 11, The displacement measurement sensor includes a displacement measurement light source that irradiates light to the processing object and a light receiving element that receives light emitted from the displacement measurement light source and reflected by the processing object. A laser processing device further comprising a dichroic mirror that reflects light from the laser device and transmits light from the light source for measuring displacement.

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